tailieunhanh - Báo cáo khoa học: Arabidopsis amidase 1, a member of the amidase signature family

Amidase 1 (AMI1), a specific indole-3-acetamide amidohydrolase, is an Arabidopsis thalianaamidase signature enzyme that catalyzes the synthesis of indole-3-acetic acid from indole-3-acetamide. Amidase signature family members catalyze a diverse range of enzymatic reactions and are found widespread in nature, for instance in bacteria, mammals, and plants. | ễFEBS Journal Arabidopsis amidase 1 a member of the amidase signature family Daniel Neu1 Thomas Lehmann1 Skander Elleuche2 and Stephan Pollmann1 1 Lehrstuhl fur Pflanzenphysiologie Ruhr-Universitat Bochum Germany 2 Lehrstuhlfur Allgemeine und Molekulare Botanik Ruhr-Universitat Bochum Germany Keywords amidase auxin biosynthesis catalytic triad modeling mutagenesis Correspondence S. Pollmann Department of Plant Physiology Ruhr-University Bochum UniversitatsstraBe 150 ND 3 55 D-44801 Bochum Germany Fax 49 234 32 18147 Tel 49 234 32 24294 E-mail Received 13 October 2006 revised 30 March 2007 accepted 11 May 2007 doi Amidase 1 AMI1 a specific indole-3-acetamide amidohydrolase is an Arabidopsis thaliana amidase signature enzyme that catalyzes the synthesis of indole-3-acetic acid from indole-3-acetamide. Amidase signature family members catalyze a diverse range of enzymatic reactions and are found widespread in nature for instance in bacteria mammals and plants. At the protein level the family members share a conserved stretch of w 50-130 amino acids the name-giving amidase signature. Elucidation of the crystal structures of a mammalian fatty acid amide hydrolase and the bacterial malonamidase E2 revealed an unusual Ser-cisSer-Lys catalytic triad in proteins of this family. In addition other members such as the amidase from Rhodococcus rhodochrous strain J1 or Sulfolobus solfataricus seem to use an accessory Cys-cisSer-Lys center. AMI1 possesses all conserved amino-acid residues of the Ser-cisSer-Lys triad but lacks the CX3C motif and therefore the Cys-cisSer-Lys catalytic site. Using a set of point-mutated variants of AMI1 and chemical modifications we analyzed the relative importance of single amino-acid residues of AMI1 with respect to substrate conversion. These experiments revealed that a specific serine residue Ser137 is essential for AMI1 enzymatic activity. We also report structural and .